Bonfires are a great way to dispose of woody material and hedge cuttings in your yard or garden. The resulting ash acts as a great homemade fertilizer for many plants as it contains potassium, phosphorus, calcium and other minerals that are required in some quantity for healthy plants.
But do roses benefit from an application of wood ash?
Wood Ash is highly alkaline pH due to the calcium content whereas rose’s thrive in soil slightly on the acidic side with a pH of anywhere between 6-7 and an optimal soil acidity of pH 6.5. Therefore you shouldn’t directly add large amounts of wood ash to the surrounding soil of established rose bushes.
However roses do benefit from the occasional light sprinkling of wood ash in the growing season before they flower. Wood ash contains a good quantity of potash which is an essential nutrient that roses need to develop flowers and produce top quality blooms.
The important thing is to know the pH of soil and how to apply wood ash correctly to minimize the effect of the alkalinity whilst still benefiting from the potash and other nutrients and minerals.
Neutralize Overly Acidic Soils before Rose Planting
If you have an area of soil where you would like to plant new roses and it has an acidity lower then pH 6 then adding half a pound of wood ash the surface of the soil and watering it in will help bring the soil back to the optimal range for roses.
It always good practice when planting new roses to test the soil first with a soil test kit to gauge the pH of your soil before planting.
Even in a small area the soil in your yard can differ in the pH level quite significantly. If the soil is particularly acidic (pH 5 or lower) then the rose’s roots will suffer and the rose could die.
However this is easily fixed you can amend the soil by adding wood ash (1 cup at a time) and retesting the soil after 4 weeks. I would recommend digging the wood ash into the soil with a fork or tilling the ash into the soil with a rotavator to help change the profile of the soil.
Only work 1 cups of ash into over acidic soil at one time. Too much wood ash in one go could change the soil to an alkaline pH and then you would have to add ericaceous compost to re-balance the affect of the ash.
Wood ash also has the benefit of not containing any seeds or roots that can develop into weeds. The intense heat of the fire renders any seeds, roots and rhizomes of both annual and perennial weeds inert.
Whereas other compost or mulch that are derived from garden waste or kitchen scraps can harbour seeds, and roots for a very long time which germinate and grow as soon as you spread the compost around your garden. This means you may have to spend more unnecessary time weeding.
Also most compost heaps will not contain potash in anywhere near the levels of wood ash so it is a great way to amend compost to be used as mulch with ash and increase the level of potash which is required in a good quantity by roses during the growing season to produce flowers.
When to Apply Wood Ash to Your Rose Bed
The best time to apply wood ash or wood ash containing compost around your roses is before the growing season, at the start of spring in April/May time. The potassium (potash) content of the wood ash promotes flower growth to give your roses the best possible bloom for as long as possible.
Applying just before or at the start of spring allows the water soluble potassium to reach the roots of your roses at the right time to promote flowering.
Like all fertilizers I would advise you avoid adding wood ash compost at the end of the summer (after August 15th) as this may promote new growth on your rose late in the season when winter is around the corner. New growth is obviously more susceptible to damage in cold weather and as soon as the first frost arrives the delicate new growth will be killed.
If you have a surplus of ash then I would advise you keep it dry for use next season or spread it elsewhere in the garden as there are other plants that will appreciate the potassium content. Lawns in particular can benefit from the addition of wood ash.
How to Apply Wood Ash to your Roses
There are only two methods of application I would recommend when fertilizing rose beds.
- You can scatter wood ash around the base of your roses in small quantities at the start of spring before flowering, however you must go sparingly because of the alkalinity. Aim for about half a cup of ash per rose bush. There is no need to rake or dig in as this could disturb the roots of your rose and interfere with the soil ecology unnecessarily. The primary nutrient of wood ash that benefits rose blooms (potash) is water soluble, so if you wash the ash in with around 2 gallons of water then the potash should reach the roots quickly, which is why it is important to apply wood ash to your roses before or during flowering.
2. The second and I think the best option is to add the wood ash to your compost pile earlier in the year and the spread the compost as mulch around your rose bed.
This relies on keeping the compost heap out under cover or at least out excessive rain as this can wash the beneficial potash from the out compost heap as it is a water soluble mineral.
Personally I keep my compost heap under a few layers of cardboard. This excludes light from the compost so weeds don’t grow from underneath and seeds don’t land into the compost and germinate.
Also when the bottom layer of cardboard rots down, it adds valuable carbon to the heap which helps balance out levels of nitrogen for more fertile compost.
But primarily I use the cardboard for maintaining the moisture balance after I add the wood ash so that the potash concentration is preserved for when I want to fertilize my rose bushes.
Mixing the ash with compost will also provide the potash and other minerals that the roses love without altering the pH of the rose bed.
Compost composed of grass clippings, leaves and kitchen scraps rots down to a neutral or slightly acidic pH mulch. This is helpful as it is in the optimal pH for roses and it negates the alkalising effects of wood ash.
It is worth restating that wood ash contains potassium, phosphorus and calcium all of which are beneficial for the growth of roses, and they’re minerals that are difficult to obtain from standard compost in organic gardening.
The benefit of adding wood ash to your compost heap to then distribute around the base of roses is that compost composed of leaf mould, grass clippings and kitchen scraps helps to improve soil structure.
Roses love organic material as this it absorbs water but also allows good drainage. This allows the roots of your rose to draw upon moisture as and when it is needed without the soil becoming water logged.
This makes the plant far more resilient in the dry weather.
For best results add a cup of wood ash every 15 inches into your compost pile. This ensures that the alkalinity will be cancelled out and the resulting compost will be at the right level of acidity for roses.
If you have any uncertainty about your soil acidity I recommend that you buy a soil test kit from amazon which measures the soil’s pH, moisture level and the amount of sunlight that spot of your garden receives per day, all of these factors are highly important for rose growing.
Apply the wood ash amended compost as mulch at the start of the growing season at around April/May.
This will allow time for potash and other nutrients from the mulch to reach the roots of the rose and stimulate the production of top quality blooms. At the start of the growing season.
Can I use Fireplace Ashes for Roses?
Fire place ashes much like wood ash will benefit your roses when applied with the right quantity. This is assuming you are burning seasoned logs with paper/fire lighter or kindling.
Ashes from different types of wood do tend to have a similar mineral and nutrient composition, and any variability between different types is negligible so you don’t need to worry about any differences between individual types of wood ash.
In fact fireplace ash may be the best way to collect ashes as you clean out your fireplace as it will be 100% dry. It is worth stating again that the key nutrient in wood ash that will benefit roses (potassium otherwise known as potash) is water soluble. This means that it will dissolve in water and effectively wash away after several spells of persistent heavy rain.
As the ash is bone dry in the fire place, you can ensure the content of valuable potash is at its highest concentration so that you can distribute it on your rose bed as and when you need to.
What About Ash from Coal or BBQ Charcoal for Roses?
Do not use the remains of coal or charcoal around your yard or garden. This isn’t specific to just roses but to all plants in your yard, particularly a vegetable garden.
This is for 2 reasons:
- Discarded coal has a much lower concentrations of nutrients compared to wood ash
- Because the coal can contain traces of arsenic and potentially other toxins.
There is some debate and ambiguity about whether these trace toxins have any significant affect on your plants but my personal advice would be to err on the side of caution and dispose of your used coals into your regular, conventional trash.
Used charcoal from your BBQ may also be contaminated with animal fat which won’t do your soil structure any favours so it’s best to stick exclusively to using wood ash around your roses.
Wood ash can benefit roses due to its abundance of potash which helps stimulate flower production. However you do need to bear in mind the alkalinity of wood ash on the soil as roses prefer a slight acidic soil of pH 6-7.
Scatter the wood ash lightly and water in during the spring or amend your compost pile with 1 cup of ash every 15 inches into the pile and distribute the compost as mulch around your rose bed. By adding the wood ash to compost it ensures to negate any alkalising effects of the the ash thanks to the fact compost decomposes to a slightly acidic or neutral pH which is perfect for roses.
If you have any doubts then I always recommend buying an inexpensive soil test kit from amazon. It will help you assess the suitability of an area you want to plant roses and takes the guess work out of the process. Best of all you can use it again and again throughout your garden.